A problem which is currently strongly felt in various fields reliant on the security of documents, and most of all in the case of checks, is the one related to the possibility of detecting or preventing forgery of the document, such as the fraudulent alteration of the amounts written on a check or the name of the recipient on the check.
Any document that represents value, particularly banknotes and checks, requires particular measures that are aimed specifically at preventing its counterfeiting and forgery by ill-intentioned individuals. The problem is particularly felt in relation to the alteration of checks for which a high level of security is required. Many checks are produced with solutions suitable to make them difficult to alter or reproduce. For example, checks may include watermarked paper that displays symbols or figures imprinted so that they are visible only if held up to the light, a silver-coated thread that is usually arranged vertically, holograms, and so forth.
Unfortunately, the forgery or alteration of business checks is relatively easy. Business checks are often printed in two printing steps. The first prints on a generic design with some security features to make a blank check. The second printing step can add the specific data like check amount, payee, date, etc. The second printing step is usually performed using a dry toner and is heat fused to the paper on a laser printer. These are often network printers or modified copiers. Forgery can be accomplished by using a knife to pick the fused toner off of the check and then re-printing the check with new payees, dates, or amounts, for example. There remains a need for detecting if a check has been tampered with and potentially forged. The same problems apply to all value-bearing documents, such as banknotes, identity documents, tickets, and so forth. The concept of the present invention is to provide for the appearance of a mark or colored blemish on the document where the alteration or forgery has occurred (e.g., by the application of pressure from a knife in scraping off the fused toner or ink).
One industry in the art, known for reproducing marks, is the concept of carbonless papers. Carbonless impact marking papers or carbonless copy papers are typically used for the transfer of images. These carbonless papers are capable of producing an image upon application of pressure. Products employing this chemistry generally contain at least two substrates (for example, two sheets of paper) and involve coating one reactant, known as a color former, on one substrate, and the other reactant, known as a developer, on another “mating” substrate. When a pressure (e.g., the force of writing) is applied to the first substrate, a copy of the writing is developed on the second substrate. Carbonless paper is often used for printed form-sets for preparing multiple copies of receipts, bills, and other business forms. It is not believed that this type of carbonless paper technology has been applied or used with a single substrate (for example, a single document) in order to detect alteration or forgery of a document. In addition, the carbonless paper technology requires a very small amount of pressure (e.g., the pressure applied from a pen during writing) to cause the marks to develop on the second substrate. It is desirous to have a system where a relatively high amount of pressure (e.g., the pressure from a knife scraping off the printed subject matter) causes the marks to develop or appear.